Etching a substrate: processes – Etching of semiconductor material to produce an article...
Patent
1996-12-09
1999-03-23
Watkins, III, William P.
Etching a substrate: processes
Etching of semiconductor material to produce an article...
428143, 428147, 428156, 428166, 428421, 428422, 216 11, 7351432, 7351436, 7351437, 361280, 257415, 438 52, C23F 100
Patent
active
058854681
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Both in use and during production, movable elements of micromechanical components, for example sensors or actuators, encounter the problem of the movable part adhering to the support. This so-called "sticking" occurs during production as a consequence of strong capillary forces during the drying of the liquids used during and after etching. When the component is used, in the event of an excessive displacement of the movable part toward the substrate, it is possible for such an intimate contact between this part and the surface of the substrate to occur that the part no longer detaches from the surface.
The publication by D. Kobayashi et al.: "Photoresist-Assisted Release of Movable Microstructures" in Jpn. J. Appl. Phys. 32, L1642-L1644 (1993) describes a method by which, using additional layers of photoresist, a movable part provided for a micromechanical component is detained in such a way that a wet-chemical etching process can take place without the movable part adhering to the support. The photoresist is subsequently removed by ashing in an oxygen plasma.
SUMMARY OF THE INVENTION
The object of the present invention is to specify a micromechanical component, in which sticking of a movable section of the surface structure to the substrate is prevented, and an associated production method therefor.
In general terms the present invention is a micromechanical component having a movable section, arranged at a distance over a substrate, of a micromechanical structure. Spacers are present on a top side, facing the movable section, of the substrate, between the movable section and the top side. The spacers are dimensioned such that sticking of the movable section to the substrate or to the spacers is prevented.
In one embodiment the spacers are made of a fluorocarbon.
The present invention is also a method for the production of a component as described above. In the method a sacrificial layer and a structure layer are applied to a substrate. The structure layer is structured in accordance with the movable section to be produced. The sacrificial layer is at least partially removed between the movable section and the substrate. Portions of a layer made of a material provided for the spacers are deposited between the section and the substrate. The layer is etched back to the envisaged spacers.
Advantageous developments of the present invention are as follows.
The layer made of a material provided for the spacers is deposited with an uneven layer thickness by utilizing the shading effect of that portion of the structure layer which is provided for the movable section.
The deposition is carried out as the divergent deposition of fluorocarbon in a plasma reactor under the action of an electric field directed toward the substrate.
The sacrificial layer is removed, with the exception of residues which remain between that portion of the structure layer which is provided for the movable section and the substrate. This prevents sticking of the movable section to the substrate or to the spacers during subsequent method steps. After etching back the layer for the spacers, these residues of the sacrificial layer are removed in a further step.
In the component according to the invention, small spacers made of a separately applied material are present on the surface of the substrate, between the substrate and the movable section of the micromechanical structure. These spacers cause the top side of the substrate to become so uneven that the movable section, that is to say the movable element of the component, can come into contact with these spacers only at a few points, thereby preventing sticking to the substrate.
These spacers are preferably produced after a sacrificial layer and a structure layer, provided for the production of the movable part, have been deposited on a substrate, the structure layer has been structured in accordance with the movable section to be produced and the sacrificial layer has been at least partially removed at least in the regions provided for the spacers. A residu
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Proceedings IEEE Micro Electro Mechanical Systems, IEEE Catalog No. 94CH3404-1, New York, "Materials Analysis of Fluorocarbon Films, for MEMS Applications", J. Elders et al, pp. 170-175.
Patent Abstracts of Japan, vol. 17, No. 91, (E-1324) 23 Feb. 1993; & JP 42 86 165 dated 12 Oct. 1992, T. Junichi et al, Minute Machine and Manufacture Thereof, 1 page.
Japanese Journal of Applied Physics, Part 2, (Letters), vol. 32, No. 11A, "Photoresist-Assisted Release of Movable Microstructures", D. Kobayashi et al, Nov. 1, 1993, pp. L1642-L1644.
Siemens Aktiengesellschaft
Watkins III William P.
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